It might already be installed

If you’re running Windows 8.1 or Windows RT 8.1 and you get updates automatically, you don’t need to do anything: Windows Update will download and install the update for you within the next few weeks. It won’t interrupt what you’re doing except to tell you that you need to restart your PC to finish the installation.

To check if the update is already installed, go to the Start screen. If you see a Search button near your account name at the top of the Start screen, you already have the update.

After the update, the Search button appears on the Start screen.

The update is gradually rolling out to everyone with a PC running Windows 8.1 or Windows RT 8.1 over a period of several weeks. If you get automatic updates but you don't see the update yet, wait a few days and check again.

Notes

If you're running Windows RT 8.1, this update is automatic. If you're running Windows 8.1 and you want to check your Windows Update settings, see Turn automatic updating on or off.

If your PC is running Windows 8 or Windows RT, open the Windows Store on your PC and update to Windows 8.1 or Windows RT 8.1. This latest update will be included. For more info, see Update to Windows 8.1 from Windows 8.

If you’re connected to the Internet over a metered connection, you might not get the update until you switch to a non-metered connection and then check manually for updates. For more info, see Metered Internet connections: FAQ.

Install the update manually

If you’re running Windows 8.1 or Windows RT 8.1 and you don’t have the update yet, you can manually check for and install the update by following these steps:

Make sure your PC is plugged in and connected to the Internet using a non-metered connection. Don’t disconnect, unplug, or turn off your PC while the update is being installed.

Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings. (If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, click Settings, and then click Change PC settings.)

Tap or click Update and recovery, and then tap or click Windows Update.

Tap or click Check now.

If updates are found, tap or click View details.

In the list of updates, select the update containing KB 2919355, and then tap or click Install.

If you're prompted for an administrator password or confirmation, enter the password or provide confirmation.

After the installation is complete, restart your PC and sign in.

Note

If you don’t see KB 2919355 in the list of available updates, you might be missing one or more required updates. Follow the previous steps to check for updates, install all important updates, particularly KB 2919442, restart your PC, and then check for KB 2919355 again.

Why you should install this update

We strongly recommend that you install
Windows 8.1 Update or
Windows RT 8.1 Update (KB 2919355). This is a critical update that is required for future updates to Windows. If you prevent it from installing or you uninstall it, you won’t get future bug fixes, security updates, and new features.
In some cases, if you uninstall this update from a new PC after signing in with a Microsoft account, OneDrive might not work as expected.

How much drive space you need to install the update

In most cases, you'll need the following amount of available drive space on your PC to download and install the
Windows 8.1 Update or
Windows RT 8.1 Update (KB 2919355) from Windows Update, depending on your version of Windows:

Windows 8.1 (64-bit version): 2 GB

Windows 8.1 (32-bit version): 0.8 GB

Windows RT 8.1: 1.1 GB

These amounts are estimates, so you might need slightly more or less available drive space for the update. To learn how to check the current space on your PC and free up space, see Tips to free up drive space on your PC.

Troubleshoot problems installing the update

If you see any of the following Windows Update errors when you try to install the
Windows 8.1 Update or
Windows RT 8.1 Update (KB 2919355), you might be able to fix the problems with these solutions. If you need more help, contact Microsoft support.

Windows Update error

What it means and how to fix it

Windows Update error

Code 0x80073712

What it means and how to fix it

This error might mean that a file needed by Windows Update is damaged or missing. Here are a few steps you can try to fix the problem:

This error might mean that a driver or other software on your PC isn’t compatible with the update. For info about how to fix this problem, contact Microsoft support.

Windows Update error

Code 0x800F0922

What it means and how to fix it

This error might mean that your PC couldn't connect to the Windows Update servers. If you're using a VPN connection to connect to a work network, disconnect from the network and turn off the VPN software (if applicable), and then try to install the update again.

The error could also mean there isn't enough free space in the System Reserved partition. You might be able to fix this problem by using third-party software to increase the size of the System Reserved partition.

Open Windows Update by swiping in from the right edge of the screen (or, if you're using a mouse, pointing to the lower-right corner of the screen and moving the mouse pointer up), tapping or clicking Settings, tapping or clicking Change PC settings, and then tapping or clicking Update and recovery.

Tap or click View your update history.

Windows Update error

Error: The update is not applicable to your computer.

What it means and how to fix it

This error might mean that your PC doesn't have the required update KB 2919442 installed. Check to make sure that all important updates, including KB 2919442, are installed on your PC. If all updates are installed, you might need to refresh your PC.

Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings.(If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, click Settings, and then click Change PC settings.)

Tap or click Update and recovery, and then tap or click Recovery.

Under Refresh your PC without affecting your files, tap or click Get started.